|Greetings from the Critique Club!
This is a well-exposed shot and meets the requirement of being in b/w...but the portrait orientation, instead of the much wider, horizontal landscape orientation, is one reason why this image did not do well. This is a photo of a tree, first and foremost, and it is simply not a lone tree.
There are many simple fixes here. First, crop your photo to landscape orientation; I can see by your settings that you used a tripod but it might have been good to reduce the depth of field so the back treeline would be out of focus and hopefully help highlight your lone tree more effectively. Also at f.11 and twilight, it is already very murky, so you want more light either with a wider aperture or longer exposure.
Finally, my favouritest thing to do in the world...change your point of view. This looks like it was shot at regular human standing eye level. If you want to isolate that tree and truly make it the only tree in the shot, be ready to squat down, or kneel or even lay belly down in the dirt and shoot up to get that one tree in the shot and no others.
Try even just one of these small techniques and see the difference it makes!
Hope this helps,